As a method for realizing database (DB) duplication for the purpose of one of countermeasures against disaster, load distribution, and so on, a method is available in which a log representing an update result of a copy source database based on a structured query language (SQL) application in a primary system is transmitted to and used in a copy destination database in a secondary system.
In such a database duplication system, a fault may occur from which self-recovery by the secondary system is not possible. In this case, by extracting DB data to be transmitted to the secondary system, transferring the extracted DB data to the secondary system, and storing the DB data transmitted from the primary system in the copy destination database, the copy destination database may be logically restored using the DB data from the copy source database.
Data synchronization techniques in a database duplication system include, for example, the technique described next. That is, a primary storage system transfers, by synchronous remote copying, write data written to a log logical disk to a secondary storage system on a recovery site. The primary storage system also transfers, by asynchronous remote copying in which the writing order is guaranteed, write data written to a DB data logical disk to the secondary storage system on the recovery site. The log logical disk and the DB data logical disk are discriminated from each other. The write data is data written to the primary storage system as a result of a transaction but is not data separately extracted for recovery or the like.